What Is Kinetic Theory In Physics/ Basic science: J S 3
KINETIC THEORY OF MATTER
J s 3 3rd term
week 6
By the end of the lesson, students should be able to:
- Justify the assumptions of Brownian on particulate movement.
- Explain molecular nature of solid, liquid and gas.
- Use kinetic theory to explain evaporation and boiling
The Kinetic Theory of Matter
The Kinetic Theory of Matter is a fundamental concept in physics that explains the behavior of matter in terms of the motion of its constituent particles.
Kinetic theory of gases
Kinetic theory of gases – states that gases consist of small particles in random motion. The kinetic particle THEORY explains the properties of the different states of matter. which includes solids, liquids and gases have different amounts of energy. They are arranged differently and move in different ways.
Property of solids
They have a fixed shape and cannot flow
The particles cannot move from place to place
They cannot be compressed or squashed
The particles are close together and have no space to move into
Property of liquids
They flow and take the shape of their container
The particles can move around each other
They cannot be compressed or squashed
The particles are close together and have no space to move into
Gases
Gases are made up of molecules. What are molecules? Molecules are the smallest unit which behaves same as the sample, i.e. they have the same chemical properties as of the sample.
Property of gases
They flow and completely fill their container
The particles can move quickly in all directions
They can be compressed or squashed
The particles are far apart and have space to move into
Changes of state
Melting and freezing
If energy is supplied by heating a solid, the heat energy causes stronger vibrations until the particles eventually have enough energy to break away from the solid arrangement to form a liquid.
When a liquid freezes, the reverse happens. At some temperature, the motion of the particles is slow enough for the forces of attraction to be able to hold the particles as a solid. As the new bonds are formed, heat energy is evolved.
Boiling and condensing
If more heat energy is supplied, the particles eventually move fast enough to break all the attractions between them, and the liquid boils. The heat energy required to convert one mole of liquid into a gas at its boiling point is called the enthalpy of vaporisation.
If the gas is cooled, at some temperature the gas particles will slow down enough for the attractions to become effective enough to condense it back into a liquid. Again, as those forces are re-established, heat energy is released.
The evaporation of a liquid
The average energy of the particles in a liquid is governed by the temperature. The higher the temperature, the higher the average energy. But within that average, some particles have energies higher than the average, and others have energies lower than the average. Some of the more energetic particles on the surface of the liquid can be moving fast enough to escape from the attractive forces holding the liquid together. They evaporate.
Sublimation
Solids can also lose particles from their surface to form a vapour. Sublimation is the direct change from solid to vapour (or vice versa) without going through the liquid stage. For example, naphthalene, dry ice of carbon(iv)oxide, Iodine crystals e.t.c
EVALUATION
State four properties of solid, liquid and gas
What are the particles of matter?
State three assumption of kinetic THEORY of gases.
Explain molecular nature of solid, liquid and gas.
- Particle Model: According to the Kinetic Theory, matter is composed of tiny particles (atoms, molecules, or ions) in constant motion.
- Particle Motion: These particles are always in motion, even in solids where they vibrate in fixed positions. In liquids, they move more freely, sliding past each other, while in gases, they move rapidly in random directions.
- Energy of Motion: The kinetic energy of particles increases with temperature. When temperature rises, particles move faster, and when temperature falls, they move slower. This relationship between temperature and kinetic energy is quantified by the equation KE = (1/2)mv^2, where KE is kinetic energy, m is mass, and v is velocity.
- Pressure and Volume: In a gas, the constant motion of particles leads to collisions with the walls of the container. These collisions create pressure. As gas particles move faster (due to increased temperature), they collide more frequently and with more force, increasing the pressure. When the volume of the container decreases, particles collide with the walls more often, also increasing pressure.
- Temperature and Pressure Relationship (Ideal Gas Law): The kinetic theory helps explain the relationship between temperature, pressure, and volume in gases, as described by the ideal gas law: PV = nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant, and T is temperature in Kelvin. According to this law, at constant volume, pressure increases with temperature, and at constant pressure, volume increases with temperature.
- Expansion and Contraction: Matter expands when heated because the increased kinetic energy causes particles to move further apart, while it contracts when cooled because the decrease in kinetic energy causes particles to move closer together.
CALCULATION OF GRAVITATIONAL FORCE: Basic Science E-Note J S 1
